Dynamic phosphorescent gel with dual supramolecular interactions for visualization of moisture monitoring

Abstract

Pure organic room-temperature phosphorescence (RTP) has attracted widespread attention due to its large Stokes shift and long luminescence lifetime. Gels, as synthetically produced soft materials, are known for their adsorption capacity, ease of preparation, and degradability. However, stimuli-responsive gels with controllable RTP emission were rarely reported. In this study, an RTP supramolecular gel enabling visualization of humidity-response was developed through construction of dual non-covalent interactions. Firstly, the assembly process of two molecules of the fluorescent compound (Upy3-BrBP) and cucurbit[8]uril (CB[8]) successfully induced RTP emission. Moreover, the complex could act as a crosslinker to connect disordered hydrogen-rich polymers into regularly ordered polymer networks, generating a supramolecular gel and significantly enhancing RTP leading to nearly pure RTP emission. The phosphorescence quantum yield increased sharply by a factor of 19.2, and the phosphorescence lifetime was extended by a factor of 8.6. More importantly, the formed supramolecular gel enables visualization of ambient humidity and its changes through RTP variation from shining green to dark blue. This RTP supramolecular gel offers a new strategy for the development of intelligent sensing materials with visual monitoring capability.